My Frozen Embryo Transfer (FET) Protocol & FAQ’s

Tomorrow I go in for a check of my lining thickness…I started taking the vivelle (estrogen patches) on 8/2 so tomorrow will by day 19 of my FET cycle…The total time on this protocol will be 36 days… If my lining is 8mm or above I will have another appointment on Thursday to do another check and start progesterone suppositories and my transfer will be 5 days from then which would be 8/28…I really hope that my lining is thick enough which has been an issue in the past but I am feeling bloated so I hope that is good news.  This protocol was really easy since there really was barely any monitoring and no injectables so that was good but a bit scary since I did not know what was going on. Wish me luck that my lining is where it should be!!!

My FET Schedule

7/31/12 – FET Consult

8/2/12 – Blood & Sonogram; Start 2 – 0.1 Vivelle Patches every other day

8/9/12 – Blood & Sonogram – lining = 5mm

8/21/12 – Blood & Sonogram – lining = ?

8/23/12 – Blood & Sonogram – Start progesterone; lining = ?

8/28/12 – Transfer?

9/6/12 – Beta?

Frequently Asked Questions

What is a FET?

Frozen embryo transfer, or FET, is an assisted reproductive technology procedure in which a previously frozen embryo is thawed and transferred it into an appropriately prepared uterus in order to have a baby.

Frozen embryo is a term for embryos that are not transferred during an IVF cycle and are deemed suitable for cryopreservation, or freezing. The best embryos are most commonly selected for transfer in fresh IVF cycles. Should suitable quality embryos remain, they can be frozen for later use. Not all cycles have embryos that are suitable for freezing. The rate of survival following thawing of frozen embryos is approximately 70%, so only good quality embryos should be frozen.

Occasionally a freeze-all cycle may be recommended. Instead of transferring an embryo following IVF, all embryos are frozen for later thawing so that the best surviving embryo can be transferred at a later time. Freeze-all cycles may be suggested for a variety of reasons such as if the woman is ill or has uterine bleeding that could result in the transfer being less likely to achieve a successful pregnancy. Other reasons to do a freeze-all are in cases where either a uterine polyp may jeopardize implantation due to its size and location, or in cases where intrauterine fluid has accumulated, lowering the probability of the embryo being able to adhere to the uterine wall. In cases of ovarian hyper-stimulation syndrome (OHSS), a freeze-all is often recommended as the risk of OHSS severity is significantly reduced if pregnancy does not occur. Still another indication for a freeze-all is in cases where pregnancy has not resulted from multiple prior fresh embryo transfers due to potential detrimental effects resulting from hormonal fluctuations or imbalances.

How is a FET cycle done?

My FET protocol does not include Lupron but simply involves the use of estrogen (vivelle patches) for 3 weeks. Once the uterine lining achieves 8mm thickness, progesterone is begun, followed by embryo transfer.

How are embryos frozen?

Cryopreservation is freezing tissue or cells in order to preserve it for the future.

• Cryopreservation is used in infertility programs to freeze and store sperm, eggs or to freeze “leftover” embryos from an in vitro fertilization cycle
• There are 2 methods currently used for freezing in IVF labs
  • Slow freezing
  • Vitrification (ultra-rapid freezing) – Most RE’s use vitrification (including mine)

Since the embryos have been cultured for five to six days, this enables the best assessment for viability and thus fewer non-viable embryos will be frozen at this stage. In the past, survival of the embryo after thawing has not been very good. In recent years, however, techniques for freezing blastocysts have improved and in selected centers the survival rate is very good. Blastocyst cryopreservation allows for the thaw and transfer of embryos on the same day.

What is Vitrification?

• To embryologists, vitrification is ultra-rapid IVF embryo freezing instead of the traditional slow freezing process
• To a science dictionary, vitrification is the process of converting something into a glass-like solid that is free of any crystal formation

How successful is FET?

There is much confusion about the ability of frozen embryos to produce pregnancy. On initial inspection, the chance for pregnancy using frozen embryos appears to be lower than the transfer of fresh embryos. On closer analysis, however, this may not be true.

Typically, when a frozen embryos transfer is performed, the embryos that were frozen were those that were not chosen for the initial fresh embryo transfer. Why not? Often, the embryologist chose the “best” embryos for the initial transfer. The embryos that remained were frozen. Some programs are very strict about the quality of the embryos they will freeze, other programs will freeze any and all remaining embryos. As in the case of fresh embryo transfer, embryo quality has a profound effect on the chance for pregnancy. If poor quality embryos were frozen, the survival rate after thawing as well as the pregnancy rate would be expected to be lower.

A second important factor is the number of embryos that are transferred. Take the example of a couple who produce four good quality embryos. Two are transferred in the fresh in vitro fertilization cycle and two are frozen. A pregnancy results and the couple delivers a baby. Later, the couple decides to attempt pregnancy again using the frozen embryos. Upon thawing, however, only one embryo survives. The frozen transfer is of a single embryo. Pregnancy rates of a single embryo are going to be lower than that seen with a multiple embryo transfer.

Studies have been performed in women who had a very vigorous stimulation of their ovaries and were considered to be at high risk for ovarian hyperstimulation syndrome (OHSS). Their physicians decided to skip the embryo transfer and instead freeze all of the embryos for later use. This significantly decreases the risk of serious or complicated OHSS. In other cases, the physicians decided to go ahead with a fresh embryo transfer anyway, despite the risk of OHSS. In this experiment, the couples in both groups have a large number of embryos and the selection of embryos for transfer was for the best embryos in each case. These studies show no difference in the pregnancy rates between fresh or frozen embryos.

We can conclude that cryopreservation does not by itself decrease the chances for pregnancy, rather it is the number of quality of embryos available that is the determining factor.